Air heating furnace for drying purposes



C. F. CULP ET L AIR HEATING FURNACE FOR DRYING PURPOSES ,Filed July 2'7, 1951 July 27, 1954 3 Sheets-Sheet l Human? lm lllllmlllln..

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July 27, 1954 c cu ET AL AIR HEATING FURNACE FOR DRYING PURPOSES Filed July 27. 1951 3 Sheets-Sheet 2 1NVENTOR$ By Cnzsrez F CULP q GEORGE A. ecu-'55 ATTORNEYS July 27, 1954 c CULP ET AL 2,684,668

AIR HEATING FURNACE FOR DRYING PURPOSES Filed July 27. 1951 3 Sheets-Sheet 3 IN V EN TORS CHESTER F CULP BY 6502s: A. Ear-"Es W? ATTORNEYS Patented July 21, 1954 UNITED OFFICE AIR HEATING FURNACE FOR DRYING PURPOSES Chester F. Culp, Piqua, and George A. Rolfes, Urbana, Ohio Application July 27, 1951, Serial No. 238,973

This invent on relates to apparatus for use particularly on farms for drying hay, grain and other agricultural products.

The invention has special relation to the provision of a portable dryer adapted for use on farms to dry harvested crops such, for example, as corn in a corn crib. hay in a barn, and the like, and it is a major object of the invention to provide such apparatus which is of. lightweight and portable construction for easy movement to different locations for use, which is simple and economical to manufacture, which is highly efiici'ent from the standpoint of both fuel and maintenance requirements, which possesses high capacity in a unit of readily small overall size and weight for easy maneuverability, and which is safe for use even in drying such highly inflammable products as hay.

It is also an object of the invention to provide a portable apparatus as outlined above which is readily adaptable to construction in different sizes and capacities for varied uses such for example as the heating of aircraft and other internal combustion engines in cold climates.

Additional objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fig. 1 is a perspective view of'a portable drying apparatus in accordance with the invention;

, .Fig. 2 is a sectional view of the apparatus taken approximately .on the line 22 of Fig. 3;

Fig. 3 is an elevational view of the front end of the apparatus;

Figs. 4 .and 5 are fragmentary sections showing the connection between the apparatus and a canvas duct for conveying the heated air to the material to be dried;

Fig. 6 is a fragmentary and diagrammatic viewin the nature of a perspective illustrating the construction and operation of the apparatus;

Fig. 12 isa fragmentary view in end eleva i n 2 further illustrating the mode of adjustment of the component parts in Fig.

Fig. 13 is a fragmentary section on the line |3-I3 of Fig. 10;

Fig. 14 is a fragmentary view similar to Fig. 2 and showing a modified construction of the apparatus; and

Fig. 15 is a fragmentary section on the line l5-l5 of Fig. 14.

Referring to the drawings, which illustrate preferred embodiments of the invention, Fig. 1 shows the general appearance and arrangement of a portable dryer unit particularly adapted for use on farms to dry agricultural products. The unit includes a main supporting frame provided with a pair of wheels 2| by means of which it can be readily transported to a desired location for use such, for example, as a corn crib, haybarn orthe like. The unit is essentially selfcontained in that it includes a burner and cooperating heat exchanger as well as a motor and fan for operating the burner and also for forcing air through the heat exchanger for heating, and the resulting heated air may be readily conducted into intimate contact with the ma terial to be dried by means of the canvas duct indicated fragmentarily at 22.

This drier unit includes an outer shell indicated generally at and shown in Fig. l as secured to the frame 20 by means of encircling straps 28. Within the shell 25 is a star-shaped wall shown as formed of a plurality of V-shaped sections which cooperate with the front end wall 3i and rear end wall 32 to form a centrally located combustion chamber 33 and a plurality of through passages 35 for the air to be heated and supplied to the material to be dried. These air passages 35 are formed between the wall sections 30 and the shell 25, and adjacent wall sections 30- also form V-shaped trough portions 36 which lie between adjacent air passages 35 and communicate throughout their entire length with the interior of the combustion chamber. Exhaust pipes 31 lead'from the rearward ends of certain of these portions" 36 to the outer atmosphere, these exhaust pipes being shown as four in number and as being curved upwardly and extending through the outer shell 25.. At the front end of the shell is areinforcing angle 38 formed to substantially circular shape. 1

The shell 25 extends rearwardly beyond the end wall 32 to house the burner unit, which includes a burner shell 40 supportedwithin a burner box it having a removable cover. 42. The burner is shown as of the jet type, with the shell 40 being cylindrical over the major portion of its length and opening at its forward end directly into the rearward end of the combustion chamber 33. The rearward end of the burner includes a curved portion 44 within a skirt portion 45 of the burner shell, and the shell is provided throughout its length with multiple openings for receiving combustion air from the surrounding portion of the burner box.

The liquid fuel enters the interior of the burner shell 44 under pressure from a jet 50, and the fuel supply system is best seen in Figs. 1 and '7. A pump 51! of any suitable positive displacement type draws the fuel from an outside supply source, not shown, preferably by way of a suitable filter 52. A solenoid valve 53 controls the flow from the pump to the supply line 55 leading to the jet 55, and this line may be provided with a pressure gauge 56 and manual valve 51. The pump is operated by .a motor 65 of any suitable type mounted on a support 5| at the rear of the frame and shown as a gasoline motor in Fig. 1 and as an electric motor in the other views, the drive connection from the motor to the pump comprising the pulleys and belt indicated gen erally at El. The spark for ignition of the fuel is supplied by a spark plug 63 mounted in the wall of burner shell 40 and connected with a transformer 64.

The air passages 35 extend the full length of the main shell from the rear end wall 32 to the front end wall 3i, and provision is made for supplying air under pressure to these passages for heating and transfer to the material to be dried. As shown, a fan 65 is mounted directly on the drive shaft of the motor 60, and a cooperating Venturi ring 66 is mounted within the open end of the shell and is bolted thereto to serve also as a reinforcement similarly to the reinforcing member 38 at the front end of the shell. In addition, provision is made for diverting a portion of the output of the fan to serve as a primary and secondary air for combustion with the liquid fuel in the burner. A pipe extends from the interior of the burner box 4| radially to the shell, and this pipe is formed with an opening ll having side walls I2 at a position closely adjacent the tips of the fan blades. Thus a portion of the air from the fan is diverted at its point of maximum velocity and is caused to flow through the pipe 10 directly to the interior of the burner box.

Improved results in operation from the standpoint of emciency and clean combustion have been obtained by the provision of baflie members arranged within the chamber box 4| forwardly of spark plug 52 to separate the interior of the burner into primary and secondary combustion areas. As shown particularly in Fig. 9, the bailles 15 are plate members which stand vertically in the burner box and have arcuate cutouts in their inner edges for engagement with the sides of the burner shell. The baffles 15 do not extend completely across the burner box but are formed to leave passages 17 therebetween above and below the shell for forward flow of air. However, with these baflles positioned as shown just forwardly of the air pipe l0, they so constrict the air flow towards the front part of the box as to maintain substantially higher pressure conditions in the rearward end of the burner shell. It appears from test results that: this arrangement gives more efiicient burning of the liquid fuel and substantially prevents clogging of the burner.

In the operation of this unit, the hot combustion gases are discharged directly to the forward end of the burner shell into the interior of the combustion chamber 33 under sufficient pressure to travel directly to the forward end of the shell chamber. However, since the forward end of the chamber is fully closed by the wall 3| the hot gases are forced to reverse their direction of flow in order to return to the exhaust outlets, and they travel in their return flow through the trough portions 36 in intimate heat exchanging relation with the star-shaped wall portions 30. As a result, these wall portions are maintained at high temperatures and act to heat the air flowing through the passages 35 to supply the desired heated air for the drying operation.

The apparatus incorporates safety controls for assuring proper operation of the burner and for preventing overheating. Referring to Figs. 7 and 8, a starter indicated generally at Bil of a suitable conventional type incorporating start and stop buttons SI and 82 is provided for controlling the motor and ignition, this starter being provided with connecting leads 83 to an outside source of current, and the motor 53 and transformer 64 are connected in parallel with the starter as shown. The control circuit for the solenoid valve 53 includes a normally closed temperature responsive switch 85 and a normally open temperature responsive switch 86 connected in parallel with a normally open manual switch 88. The switch 86 .acts as a flame detector and. is located in heat sensing relation with the combustion chamber as shown in Fig. 7, and the switch 85 acts as a temperature limit control and is located adjacent the forward end of one of the air passages 35. Since the switch 88 is open when the apparatus is not operating and is cool, the by-pass switch 88 is used to complete the operating circuit to the solenoid valve at the start of the operation and is held closed until sufficient heat is developed to close switch 85 and maintain the circuit to the valve.

Thus at the start of the operation when the unit is cold, the motor is set in operation by pressing the start button ill. At the same time ignition current will be supplied to the spark plug 63, but since the switch 86 is open, the oil valve 53 will remain closed. If the fuel pump 50 requires priming, this is done while valve 53 is still closed, and then the push button switch 88 is closed to complete the operating circuit to valve 53. The oil therefore begins to flow and the burner starts, but the operator should hold switch 88 closed for a sufficient interval for the temperature in the combustion chamber to reach a level at which switch 85 will close, this ordinarily requiring only about one minute. The pressure gauge 53 indicates whether or not the pump and valve are in proper operation, and if no pressure is shown on the gauge, both the pump and valve should be checked to determine whether either is not in operating condition.

The unit will continue to operate so long as the temperature of the heated air does not rise above the range at which switch 85 will open or so long as nothing happens to reduce the temperature in the combustion chamber below the range at which switch 86 closes. Thus if for example there should be some obstruction to the free discharge of the heated air so that the temperature adjacent switch 85 rises above a safe level, this switch will open, breaking the current tothe solenoid valve 53 and thus causing this valve to close and discontinuing the supply of oil to the burner. Similarly in the event of improper combustion or wire I26.

due to causes such as dirt in the fuel, low pressure, poor ignition or fouling of the jet, the re- Sulting drop in the temperature of the combustion chamber will cause switch 86 to open and thus effect closing of the fuel oil.

This unit as shown in the drawings is designed for especially convenient and economical construction from simple sheet metal parts. Referring particularly to Figs. 10 to 13, the V-shaped sections 30 are initially formed separately, and similarly the shell 25 is shown as formed of separate sections lilo formed with a channeled portion IBI along one edge and with a simple flange I62 along its opposite edge. In the assembly of these sections as shown in Fig. 12, adjacent edge portions of two V-sections 3i? and the flange portion IE2 of one shell H30 are inserted together into the channel portion HM of the next shell section as shown in Fig. 12, and the channel Ill! is then crimped or t erwise treated to secure these assembled parts to ether as indicated at I05, highly satisfactory results having been ob tained by performing this operation with a tool such as a button punch of conventional type which compresses the parts to form dimples I at spaced intervals along the joint.

The front end wall 3! of the unit is shown as formed of a pair of circular disks Hi] and III of sheet metal, which are spot welded together at points H2 spaced inwardly of their outer peripheries, and the outer disk IIEI is of slightly larger diameter, for example about inch as shown; The end walls of the trough portions 36 are formed of generally triangular plates H5 of sheet metal each of which includes a tongue portion H6 at its inner end arranged for insertion between the end wall disks III? and III for spot welding thereto as indicated at II! in Fig. 10. The side edges of each plate I I5 are formed with flanges no, and the ends of each of the V-sections 30 are doubled back twice as'shown in Fig. 13 to provide a recess for receiving the flanges I20 and also to form a flange I ZI adapted to be foldedover the outer face of the plate H5 and thus to lock these parts effectively together. This construction has the advantage. of facilitating manufacture of the unit in comparatively small parts for easy fabrication as well as facilitating quick and easy assembly to provide a rigid structure while still maintaining desired light weight. The construction of the rear end wall 32 is substantially the same as front end wall 3! except the center disks are cut out to receive the burner box, and certain of the end plates are similarly cut out for connecting theexhaust pipes 37.

In addition to its function in reinforcing and stiffening the end of the shell 25, the angle 38at the forward end of the unit serves as a convenient attaching device for the canvas duct 22. Referring to Figs. 4 and 5, the duct includes a draw string I25, and in initially attaching it to the dryer unit, the end of the duct is drawn over the angle 38 and is tied thereto by means of a cord The end portionof the duct is then doubled back as shown in Fig. 5 to the outer face of the angle 38, after whichthe draw string I25 is tightened to provide the desired firm but easily detachable connection. It will'also benoted 35 before it reac hes duct 22;, andalso to prevent possible'overheating of the duct such as could occur if it were unduly close to the wall 3 I, satisfactory results having been obtained with a depth 6 of about 6 inches'between wall 3| and the outer end of the shell.

Figs. 14 and 15 illustrate a construction of dryer in accordance with the invention which is in large measure similar to that shown in Figs. 1 to 13, as indicated by the similar reference characters for corresponding parts, and which also incorporates means for effecting preheating by the exhaust gases of the air supplied to the burner for combustion. Thus instead of leading directly to the atmosphere similarly to the exhaust pipes 31, the exhaust pipes I30 are all conncctcd with an exhaust manifold I3I which surrounds the burner box I32, and at the rear end of the unit the exhaust manifold connects with a large exhaust duct I leading to the outer at mosphere. Within the exhaust duct I35 is a pipe I which corresponds to the pipe Ill in the other views and serves as a conduit for air to the burner box and burner. A pipe MI leads from the pipe I46 rearwardly through the exhaust duct I35 and opens in close relation with the tips of the fan blades as shown.

With this construction as shown in Figs. 14 and 15, the air for heating and drying is supplied by the fan as above described to the open rear ends of the air passages 35, and since the passage MI is directly in front of the fan, it intencepts a portion of the output of the fan discharged from the tips of the fan blades and supplies this diverted air to the burner for combustion. The combustion gases from the burner are discharged forwardly into the combustion chamber where they travel to the front end of the unit and then reverse their direction of flow and pass to the exhaust manifold, and as these gases exhaust to atmosphere through the duct I35 they how in heat exchanging relation around the outside of the air inlet pipe I46 to provide effective preheating of the combustion air for more efficient burning. Furthermore, with the exhaust manifold I3I also surrounding the burner box I32, the air for combustion is still further heated. and this contributes to thedesired conditions for clean combustion with minimum tendency to fouling of the burner by incomplete combustion and depositrof carbon on the burner shell.

In addition to its advantages of lightweight and simple construction andready maneuverability, the dryer of the invention offers important practical advantages for farm use. For example, a unit of a'given size and full capacity can employ fans'of different sizes, such as the farmer may already have on hand, by merely providing a Venturi ring 66 of the appropriate diameter for the fan to be used. Similarly the mounting arrangement for the motor in this dryer is readily adaptable to use with an internal combustion or electric motor which the farmer may already have. The automatic operation of this unit is also a major practical advantage for farm use, it being noted that with the controls provided as described, initial ignition and con tinued operation are maintained automatically with no match being required for starting the burner, and positive provision beingv madefor discontinuing operationin the event of overheating, cloggingof the burner orfuel supply,'or like undesirable conditions. It will also be noted that if it is desired to operatethc unit Without heating the discharge air, this can be done fields of use. For example, with the unit constructed as shown in an overall diameter of the order of 45 inches and an overall length for shell 25 of the order of 8 feet, the other parts being correspondingly proportioned, the effective flow area for the heated air is square feet and the effective heat exchanging surface for this air is approximately 175 square feet, and a total air flow of from 10,000 to 30,000 cubic feet per minute is readily obtainable by suitable variation of the motor speed. The jet burner show-n in the drawings will operate satisfactorily over a fuel consumption range of from approximately 3 to 12 gallons per hour to give correspondingly wide control over the extent to which the drying air is heated. These proportions give highly satis factory operating conditions and results for farm use as described, but it will be readily apparent that these sizes and capacities can varied as desired for different uses of the unit, and particularly that similar units of smaller sizes can be readily produced for uses such as the preliminary heating of airplane and other internal combustion engines in cold climates.

While the forms of apparatus herein described constitute preferred embodiments of the inven tion, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which i is defined in the appended claims.

What is claimed is:

1. Air heating apparatus of the character described comprising a tubular outer shell having forward and rearward ends, a plurality of substantially V-shaped wall sections extending 1ongitudinally within said outer shell and arranged to form a-combustion chamber of substantially star-shaped cross section within said shell and to provide a corresponding plurality of air passages of generally V-shaped section between said wall sections and said shell, the interior of said combustion chamber being substantailly unobstructed with said wall sections forming troughs of V-section opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said shell in position to discharge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of flow and to return toward the rearward end of said cham her through said troughs in heat exchanging relation with said wall sections, said end wall being of substantially the same star shaped configuration as said combustion chamber to leave open the forward ends of said air passages for free now of air therethrough, means communicating directly with the rearward end of at least one of said troughs for exhausting said reversed oombustion gases, and means operatively associated with said shell for forcing air through said air passages for heating.

2. Air heating apparatus of the character described comprising a plurality of initially separate V-shaped wall sections extendng longitudinally of and arranged about a central axis to form a combustion chamber of substantially starshaped cross section, the interior of said combustion chamber being substantially unobstructed with said wall sections forming troughs of V-sec tion opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said combustion chamber in position to discharge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of flow and to return toward the rearward end of said chamber through said troughs in heat exchanging relation with said wall sections, wall means forming an outer shell connecting the outer edges of said wall sections to form with said wall sections a corresponding plurality of air passages extending between said troughs, said end wall being of substantially the same star shaped configuration as said combustion chamber to leave open the forward ends of said air passages for free flow of air therethrough, means communicating directly with the rearward ends of certain of said troughs for exhausting said reversed combustion gases, and means operatively associated with the rearward ends of said air passages for forcing air through said air passages for heating.

3. Air heating apparatus of the character described comprising a plurality of initially separate V-shaped wall sections extending longitudinally of and arranged about a central axis to form a combustion chamber of substantially starshaped cross section, the interior of said combustion chamber being substantially unobstructed with said wall sections forming troughs of V- section opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said combustion chamber in position to discharge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of flow and to return toward the rearward end of said chamber through said troughs in heat exchanging relation with said wall sections, a plurality of initially separate outer wall sections each proportioned to connect the outer edges of one of said V-shaped wall sections, means securing all of said wall sections together to form a plurality of enclosed air passages extending between said troughs, said end wall including V-sh-aped portions closing the adjacent ends of said troughs while leaving open the forward ends of said air passages for free flow of air therethrough, means communicating directly with the rearward end of at least one of said troughs for exhausting said reversed combustion gases from said troughs, and means operatively associated with the rearward ends of said air passages for forcing air through said air passages for heating.

4. Air heating apparatus of the character described comprising a tubular outer shell having forward and rearward ends, a plurality of substantially V-shaped wall sections extending lon gitudinally within said outer shell and arranged to form a combustion chamber of substantially star-shaped cross section within said shell and to provide a corresponding plurality of air passages of generally V-shaped section between said wall sections and said shell, the interior of said combustion chamber being substantially unobstructed with said wall sections forming troughs of V section opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said shell in position to dis-charge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of flow and to return toward the rearward end of said chamber through said troughs in heat exchanging relation with said wall sections, said end wall being of substantially the same star shaped configuration as said combustion chamber to leave open the forward ends of said air passages for free flow of air therethrough, a plurality of exhaust outlets connecting directly with the rearward ends of a spaced corresponding plurality of said troughs for exhausting said reversed combustion gases from said combustion chamber, and means operatively associated with said shell for forcing air through said air passages for heating.

5. Air heating apparatus of the character described comprising a tubular outer shell having forward and rearward ends, .a plurality of substantially V-shaped wall sections extending longitudinally within said outer shell and arranged to form a combustion chamber of substantially star-shaped cross section within said shell and to provide a corresponding plurality of air passages of generally V-shaped section between said wall sections and said shell, the interior of said combustion chamber being substantially unobstructed with said Wall sections forming troughs of V-section opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said shell in position to discharge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of ilow and to return toward the rearward end of said chamber through said troughs in heat exchanging relation with said wall sections, said end wall being of substantially the same star shaped configuration as said combustion chamber to leave open the forward ends of said air passages for free flow of air therethrough, means connected with said burner for supplying fuel thereto, a conduit leading to said burner for supplying air thereto for mixture and combustion with said fuel, means communicating directly with the rearward end of at least one of said troughs for exhausting said reversed combustion gases, said exhaust means and said conduit being arranged in heat exchanging relation to effect preheating of said combustion air, and means operatively associated with said shell for forcing air through said air passages for heating.

6. Portable air heating apparatus of the character described for drying purposes and the like, comprising a mobile base frame, a tubular outer shell mounted on said base frame and having forward and rearward ends, a plurality of substantially V-shap-ed wall sections extending longitudinally within said outer shell and arranged to form a combustion chamber of substantially starshaped cross section within said shell and to provide a corresponding plurality of air passages of generally V-shaped section between said wall sections and said shell, the interior af said combustion chamber being substantilly unobstructed with said wall sections forming troughs of V- section opening directly into the resulting unobstructed central portion of said chamber, a burner supported centrally of the rearward end of said shell in position to discharge hot combustion gases generally axially into said combustion chamber, an end wall closing the forward end of said combustion chamber to force said combustion gases to reverse their direction of flow and to return toward the rearward end of said chamber through said troughs in heat exchanging relation with said wall sections, said end wall being of substantially the same star shaped configuration as said combustion chamber to leave open the forward ends of said air passages for free flow of air therethrough, means communicating directly with the rearward end of at least one of said troughs for exhausting said reversed combustion gases from said troughs, and means including a fan and motor mounted on said base frame at the rearward end of said shell for forcing air through said air passages for heating.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,058,254 Pederson Oct. 20, 1936 2,087,393 Wilson July 20, 1937 2,141,649 Grill Dec. 27, 1938 2,205,451 Woolery June 25, 1940 2,263,098 Mueller Nov. 18, 1941 2,374,203 Holthouse Apr. 24, 1945 2,401,330 Breese June 4, 1946 2,448,595 I-Iolbrook Sept. 7, 1948 2,485,207 Logan Oct. 18, 1949 2,555,842 DeLancey June 5, 1951 2,579,507 MacCracken Dec. 25, 1951 FOREIGN PATENTS Number Country Date 923,479 France Feb. 17, 1947 

